The invention relates to a forming fabric for the wet end of a papermaking machine, comprising a one-layered or multi-layered fabric of metal or plastic material provided at its edges or in the region thereof which is a highly abrasive area with a reinforcement against abrasion.
Such a kind of forming fabric is used for the manufacture of paper and is running as an endless belt through the rolling system of the wet end of the papermaking machine in order to dewater the fiber suspension so that a fiber web is formed and transported to the pressing part of the paper machine. During that operation a fabric may be moved with velocities up to 2,000 m/min. Because of the surface contact with the dewatering elements and the rolls of the rolling system these fabrics become worn, i.e. they are used up.
It was found out that the abrasion or the wear of these fabrics is independent from the kind of their construction and is occuring particularly quickly mainly in a stripe-like area adjacent to the edges of the fabric and parallel to them. This area of high abrasion which is called highly abrasive region (HVZ) is therefore a factor essentially contributing to the life time of such kind of fabrics. If the fabrics have reached a definite degree of abrasion it is likely that they crack in cross direction so that they cannot longer be used and must be replaced by new ones. The consequence of such a wear is therefore not the damage of the fabric per se but the stop of the machine and the loss of production output during the time in which such a fabric is replaced.
In order to increase the wear resistance of the highly abrasive regions it has already been proposed to weave into the fabric within these regions additional abrasive threads. This kind of enforcement, however, is disadvantageous therein that those threads must already been woven into the fabric during its manufacture. Because of the fact that the papermaking machine fabrics are of different widths these enforcement threads must be replaced for each fabric having an other width. For that purpose expensive readjustment operations are necessary. Moreover, the positioning of the enforcement threads during the weaving operation is also defining the width of the fabric. This means that weaving defects arising very often in the region of the weaving edge cannot be avoided by the styling of the fabric. Therefore, an enforcement of the highly abrasive regions by means of additional wearing threads has been proven to be rather ineconomical and is therefore performed only in special cases.